1. Field of the Invention
The present invention relates to a diffusion plate; particularly to a diffusion plate on which two different kinds of patterns are disposed.
2. Description of the Prior Art
In recent years, the conventional cathode ray tube display (commonly called CRT display) has been gradually replaced by liquid crystal display (LCD). The main reason is that the LCD releases far less radiation than the CRT display. Moreover, the production cost of LCD drops significantly in the recent years. In general, the LCD includes a backlight module and a liquid crystal panel. The backlight module mainly aims to provide a light source for the LCD.
The backlight module generally includes a diffusion plate consisting of transparent polymer which is doped with pluralities of optical diffusion particles which can diffuse light generated by cold cathode fluorescent lamps (CCFLs) in order to reduce impact on display quality resulting from illumination shade generated by CCFLs. Without the diffusion plate, there will be visible bright and dark strips on the display surface. In the earlier time, the diffusion plate is a plane structure. As the technology advances, the diffusion plate with patterns disposed on the emission surface has been developed to further improve the display quality.
Refer to FIG. 1 for a front view of a diffusion plate with patterns disposed on the emission surface. There are pluralities of optical diffusion particles inside the diffusion plate 100 in order to diffuse light. The higher concentration of the optical particles there is, the better diffusion effect it is, and the lower transmittance it is. In the present diffusion plate, the transmittance of the diffusion plate 100 is 60%. There are pluralities of patterns 120 disposed on the emission surface 110 of the diffusion plate 100. When light passes through the patterns 120, the travel direction of light changes hence can reduce impact on display quality resulting from the illumination shade generated by CCFLs. However, the diffusion effect of the diffusion plate 100 is not ideal yet. As a result, at least two diffusion films are disposed on the diffusion plate 100 of a prior backlight module to diffuse light more uniformly.
How to make the diffusion plate fully generate desired diffusion effect is an issue remained to be resolved in the industry.